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Nylon screws, bolts, and nuts are gaining popularity. Available in all metric sizes, they are often found in appliances, electronics, and even industrial-strength uses such as production equipment and automobiles. Threaded nylon metric fasteners can connect and clamp a variety of materials commonly used in construction and manufacturing processes, such as wood, metal, plastic, etc. But, just because they can be used for a particular application does not mean they should be used.

So how do you decide whether nylon bolts and screws offer a viable alternative to more traditional metallic fasteners? The key is to understand nylon’s unique characteristics and the impact they will have on the job conditions and application.

When looking for ways to reduce waste, cost-conscious and environmentally aware manufacturers and consumers may consider reusing metric bolts and screws. But not all bolts and screws can be safely and effectively reinstalled after being removed from an assembly or component. In fact, an unequivocal “yes” is never the answer to the question of whether a fastener can be reused. Depending on the situation, the answer is always either “no” or “it depends.”

No

High-strength bolts that have been pre-tensioned into their proof load range – the point at which they permanently deform and do not “snap back” when relieved from their loads – should not be reused. This is the case in many applications, as structural and other bolts used in the manufacturing, construction, and automotive industries are commonly tightened to a torque value that creates a sufficient clamp force to prevent joint failure.

Tamper-proof screws are designed to prevent the dismantling of the products they hold together for safety and/or security reasons. Design developments have made it both difficult to unscrew some fasteners, and easier to determine if a screw has been interfered with. These “tamper-resistant” and “tamper-evident” options have an important place in making products such as electronics, safety devices, security systems, etc., safer, more secure, and less susceptible to vandalism and unauthorized “adjustments.”

The Tamper Resistant Design

Tamper-resistant screws are labeled as such, because their unconventional drive slots require specialized tools to engage and turn them. Holes, notches, and odd geometric shapes are commonly used as drive slots, and can only be driven with their corresponding tools. The theory is that thieves and vandals may keep slotted and Phillips screwdrivers among their burglary tools as a matter of course, but they are unlikely to have access to spanner or Torx drivers when the opportunity for malfeasance arises.

Tightening a nut onto a bolt causes the bolt to stretch slightly. Much like a spring, the bolt resists this stretching, and its tendency to return to its natural state creates clamping action between, say a cylinder head and a manifold, or two pieces of sheet-metal housing.

It is critical to the component’s operation that the amount of tension created holds the parts together strongly enough to prevent their separation by outside forces such as the machine’s vibration, the load stress generated during operation, gasket creep, temperature fluctuations, and more. Too much torque, however, can stretch the fastener too much, to the point where it chips, breaks, or yields. Bolts and screws are rated by their “proof load” – how much tension they can withstand before they fail. As a rule of thumb, torque a “clamp load” (also known as “preload”) 75 percent to 90 percent of the proof load is optimal.

Some things have been around so long that it’s easy to forget that there was a time they didn’t exist. These items fill their need so easily and so completely that we can’t imagine a time when people had to get by using other means. One of these items is the “kep” nut. This nut has been around for nearly a century, and many assemblers couldn’t imagine life without it.

A Little History
The kep nut was invented in 1923 by Shakeproof Screw and Nut Lock Company. The “kep” in kep-nut comes from the name Sha(kep)roof. Now owned by Illinois Tool Works (ITW), the kep nut revolutionized manufacturing and assembly just as assembly lines were taking off. Continue reading

When it comes to keeping things together, engineers, designers, and builders overwhelmingly choose metric machine screws. They’re in everything from kitchen cabinets to deep-space probes. Given the wide variety of things put together with metric machine screws, it’s no surprise that there is such a wide variety of metric screws to choose from. Learn about the different types of metric machine screws and when to use them.

The establishment of the International Organization for Standardization (ISO) is based on the need to facilitate international trade by promoting development of universal standards. Having been in place for over a decade now, the ISO 9001:2008 Certification is a universal method used by both customers and companies to control the quality of output.

It is a framework of business management ensuring continued improvements in all aspects of the business. The external assessment on a regular basis ensures maintenance of these business practices.

Whether you’re a part-time hobbyist or a seasoned mechanic, there comes a time when you have an unidentified hole, bolt, or screw. To finish your assembly, you need to know exactly what size fastener you have, or what size fastener you need. The “guess and test” method can damage the threads on the fastener and in the hole. Worse yet, you could end up with something that seems to fit, but isn’t really the right size. When that happens, mechanical failure becomes a real risk.

Fortunately, screw thread callouts are a standardized system for determining the size, thread pitch, and length of a machine screw or hole. With this information, you can quickly get all of the information you need to ensure that your fastener fits perfectly into your assembly.

Set screws are one of those smaller metric fastener components that aren’t given as much attention as they deserve.

In spite of their lack of fame, they are available in a wide variety of different fabrications. They are also used in a variety of different applications ranging from simple tasks such as installing a door knob, to more complex ones like working on a space shuttle.

Any time an object needs to be affixed to some sort of shaft, a set screw is likely to be utilized. However, given the wide variety of applications that use set screws, you want to make sure that you are using the right one for your specific application.

Bill’s company designs self-checkout systems used in grocery stores. He chooses Mr. Metric for his unique metric fastener needs because he requires unique and hard to find Self-Tapping Screws that can’t be found in other hardware stores.

Bill also has a great deal of trust when ordering metric fasteners from Mr. Metric. He knows that even in a time crunch, we’ll come through.